React Hooks multiple alerts with individual countdowns

Question

I've been trying to build an React app with multiple alerts that disappear after a set amount of time. Sample: https://codesandbox.io/s/multiple-alert-countdown-294lc

import React, { useState, useEffect } from "react";
import ReactDOM from "react-dom";

import "./styles.css";

function TimeoutAlert({ id, message, deleteAlert }) {
  const onClick = () => deleteAlert(id);
  useEffect(() => {
    const timer = setTimeout(onClick, 2000);
    return () => clearTimeout(timer);
  });
  return (
    <p>
      <button onClick={onClick}>
        {message} {id}
      </button>
    </p>
  );
}
let _ID = 0;
function App() {
  const [alerts, setAlerts] = useState([]);
  const addAlert = message => setAlerts([...alerts, { id: _ID++, message }]);
  const deleteAlert = id => setAlerts(alerts.filter(m => m.id !== id));
  console.log({ alerts });
  return (
    <div className="App">
      <button onClick={() => addAlert("test ")}>Add Alertz</button>
      <br />
      {alerts.map(m => (
        <TimeoutAlert key={m.id} {...m} deleteAlert={deleteAlert} />
      ))}
    </div>
  );
}

const rootElement = document.getElementById("root");
ReactDOM.render(<App />, rootElement);

The problem is if I create multiple alerts, it disappears in the incorrect order. For example, test 0, test 1, test 2 should disappear starting with test 0, test 1, etc but instead test 1 disappears first and test 0 disappears last.

I keep seeing references to useRefs but my implementations don't resolve this bug.

---

With @ehab's input, I believe I was able to head down the right direction. I received further warnings in my code about adding dependencies but the additional dependencies would cause my code to act buggy. Eventually I figured out how to use refs. I converted it into a custom hook.

function useTimeout(callback, ms) {
  const savedCallBack = useRef();
  // Remember the latest callback
  useEffect(() => {
    savedCallBack.current = callback;
  }, [callback]);
  // Set up timeout
  useEffect(() => {
    if (ms !== 0) {
      const timer = setTimeout(savedCallBack.current, ms);
      return () => clearTimeout(timer);
    }
  }, [ms]);
}

Answer 1

You have two things wrong with your code,

1) the way you use effect means that this function will get called each time the component is rendered, however obviously depending on your use case, you want this function to be called once, so change it to

 useEffect(() => {
    const timer = setTimeout(onClick, 2000);
    return () => clearTimeout(timer);
  }, []);

adding the empty array as a second parameter, means that your effect does not depend on any parameter, and so it should only be called once.

Your delete alert depends on the value that was captured when the function was created, this is problematic since at that time, you don't have all the alerts in the array, change it to

const deleteAlert =  id => setAlerts(alerts => alerts.filter(m => m.id !== id));

here is your sample working after i forked it https://codesandbox.io/s/multiple-alert-countdown-02c2h

Answer 2

well your problem is you remount on every re-render, so basically u reset your timers for all components at time of rendering.

just to make it clear try adding {Date.now()} inside your Alert components

      <button onClick={onClick}>
        {message} {id} {Date.now()}
      </button>

you will notice the reset everytime

so to achieve this in functional components you need to use React.memo

example to make your code work i would do:

const TimeoutAlert = React.memo( ({ id, message, deleteAlert }) => {
  const onClick = () => deleteAlert(id);
  useEffect(() => {
    const timer = setTimeout(onClick, 2000);
    return () => clearTimeout(timer);
  });
  return (
    <p>
      <button onClick={onClick}>
        {message} {id}
      </button>
    </p>
  );
},(oldProps, newProps)=>oldProps.id === newProps.id) // memoization condition

2nd fix your useEffect to not run cleanup function on every render

useEffect(() => {
  document.title = `You clicked ${count} times`;
}, [count]); // Only re-run the effect if count changes

finally something that is about taste, but really do you need to destruct the {...m} object ? i would pass it as a proper prop to avoid creating new object every time !